Froth flotation of iron ores



Patented Feb. 15, 1949 UNITED STATES PATENT OFFICE Herkenhoff, Stamford,Conn., American Cyanamid Company,

assignors to New York,

N. Y., a corporation of Maine No Drawing. Application February 14, 1944,Serial No. 522,268

Claims.

1 This invention relates to the beneficiation of iron ores by frothflotation.

In the past, iron ores have presented a very serious problem to the oredressing engineer. There are many collectors, for example, of the fattyacid type which will float iron ore, but the mere flotation is notsufficient. The ore commands so low a price and the requirements forgrade are so high that the ordinary froth flotation process with anioniccollectors will not give results which are commercially useful.

In our Patents Nos. 2,385,054, September 18, 1945; 2,410,376 and2,410,377, October 29, 1946, we have described processes in whichcertain types of promoters containing sulfonic or sulfate groups havebeen used in conjunction with acid treatment of the iron ore. Theseapplications, of which the present application is a continuation inpart, represent three particular groups of promoters which can be usedwith acid treated iron ore.

According to the present invention we have found that iron ore can beeffectively beneficiated by acid treatments under specified conditionswith sulfonated promoters obtained by sulfonating the residues from therefining of glyceride oils or fatty acids. These residues are of twogeneral types, the so-called foots, which are products that settle outin the refining of oils by chemical means, and the pitches or stillbottoms which are residues from the refining of fatty acids bydistillation. These residues are characterized by a definite butrelatively low fatty acid content associated with other organic materialsuch as glyceride oils, proteinaceous material, neutral oils, and thelike. The distillation residues, in addition, contain many products ofpartial decomposition such as carbon, cracked glyceride oils and otherproducts. The chemical composition of these residues is not constant andis not completely known as they are a mixture of a large number ofimpure compounds. The general characteristic, however, is a relativelylow fatty acid content, the fatty acid bein much lower than ordinaryfatty acids or acid oils and, in many cases, is only a minorconstituent, particularly in the case of distillation residues.

When the iron ore is conditioned at high solids, preferably 60-70%, witha strong acid having a dissociation constant greater than 10- insufficient quantities so that when diluted to froth flotation densitywithout neutralization, a pH of 1.5-5.5 is obtained, the ore can befloated with the sulfonated residues from the refining of glyceride oilsand fatty acids to produce concentrates of satisfacory iron content withhigh recoveries.

The term sulfonated is used in its general sense to describe a productobtained by the chemical reaction of sulfuric acid or other sulfonatingagents such as chlorsulfonic acid with the residue. This produces,normally, a mixture of sulfonates and other acid sulfur containingcompounds such as sulfonated compounds where double bonds are present.It is not intended to be used in a narrow sense that all of the sulfurcontaining compounds are true sulfonic acids or salts thereof.

The acid used in the treatment is not critical. Many strong acids whichdo not have an anion that adversely affects flotation, may be used.Acids weaker than those having a dissociation constant of 10- are notsuitable. The amount of acids to be used will vary with dilferent acidsand to some extent with different iron ores. In every case suflicientacid must be used to produce enough free hydrogen ions so that ondilution to froth flotation pulp density a pH of from 1.5- 5.5 results.In general, larger amounts of acids produce high grade but a falling 01fin recovery while smaller amounts produce falling oil in grade andsometimes also in recovery. The conditioning itself is at high solidsbut in practice the acid concentration generally is determined bymeasurement after dilution to flotation pulp density.

'The pH measurements after dilution are, of

course, definite numerical measures. The dilution from pulp densityduring conditioning to flotation pulp density without neutralizationchanges the pH but little and in general raises the pH by about 0.5 to1.0. The measurement after dilution will, therefore, be used in thepresent specification and claims because it is the convenient practicalmethod for large scale use. It should be understood that the particularpH of the flotation circuit itself is relatively less important. Withsome promoters and some ores, it is feasible after conditioning toeffect considerable neutralization without serious adverse effects inflotation. It is the acid strength during the conditioning and not inthe flotation circuit which appears to be the most important singlefactor.

While it is an advantage of the present invention that the range ofacidity in conditioning is not critical, nevertheless with mostpromoters and most iron ores we find that the best results are usuallyobtainable with acid strength which will dilute to flotation pulpdensity giving a pH from about 2-3. In every case, of course, the oredressing engineer will choose the amount of acid giving optimum resultswith the particular reagent combinations and ore with which he isdealing.

The amount of the collector used is not critical and in general willVary from amounts somewhat less than 1 lb. up to 5 or 6 lbs. per ton ofore. In some cases where the residue is very low grade larger amountsmay be necessary up to a maximum of about 10 lbs. The larger amounts arenot a serious economic deterrent because of the extremely low price ofthe residues in normal times, most of them having hardly more than fuelvalue.

In every case only the optimum amount of collector will be chosen.However, the optimum amount is practically never critical and slightvariations do not produce disastrous effects. This is a very realoperating advantage because many of the commercially attractivecollectors such as petroleum sulfonates and sulfonate residues are ofindeterminate nature and vary from batch to batch.

Conditioning at high solids, which is an important feature of thepresent invention, often presents a problem of distribution of thecollector over the ore particles. This is particularly acute where thecollector is not readily dispersible in water or on the other hand incertain cases where the collector is very soluble. In such cases anoiling agent may profitably be used as an adjunct. It is an advantage ofthe present invention that the character and amount of the oiling agentis not critical. Hydrocarbon oils such as fuel oil give excellentresults and their low price makes them very attractive in mostlocations. However, other oils such as glyceride oils, for example,coconut oil, linseed or cottonseed oils, work satisfactorily and certainfatty acids of oily nature may also be used. The amount of oiling,however, depends very largely on the particular collector used and mayvary from a small amount up to several pounds per ton. With everyreagent combination there is an optimum range of oiling agent. Thisrange is not critical and is not the same with different collectors. Inevery case, of course, the range for optimum results should bedetermined with the desired collector, but once determined, no operatingdifficulties result because the range is broad enough to take care ofordinary fluctuations in operation. The elimination of the necessity forcritical control of the operation is an important practical advantage.

The acids which can be used are numerous and, j

the acid must alter the'surface of the iron oxide particles but thenature of the alteration is not susceptible to exact determination. Theoiling agents also may perform several functions. It is reasonablyassured that one of the main, and, perhaps in most cases, the mainfunction is that of distributing the collector over the iron oreparticles. It is probable that in most cases the oiling agent may alsobeneficially modify the froth. This is directly observed with certainwater soluble petroleum sulfonates and may be a factor in many othercombinations.

While conditioning at high solids, which is a feature of the presentinvention, permits using collectors which are not dispersible in water,it is, nevertheless, desirable where possible to use water dispersions.In some cases some of the collectors may be dispersed in hot water, andthese dispersions or solutions make the feeding of the reagent mucheasier and are preferred where the nature of the collector permits theformation of such dispersions.

It is not necessary to use a single type of collector. Mixtures may beprofitably employed and in some cases oiling agents are also Weakcollectors for iron. Mixture of oil soluble and water soluble petroleumsulfonates are particularly important.

The problem of slime is not greatly different in the process of thepresent invention than in the general run of flotation processes. Here,as elsewhere, slime is never desirable. However, it is an advantage ofthe present invention that it is not peculiarly critical as far as slimeis concerned and it is possible to operate with undeslimed ore or, whichis more important, with ore which has been only partially deslimed, thuspermitting more economical desliming procedures. The effect of slime isnormal and manifests itself primarily in added consumption of reagent.As many of the reagents are fairly cheap it is sometimes desirable touse relatively economical desliming procedures which do not remove theslime completely and such procedures are permissible by reason of therelative lack of sensitivity of many of the reagents of the presentprocess to the presence of small amounts of slime. More involveddesliming procedures, such as those employing a polishing or scrubbingof the ore particle followed by desliming, are not normally necessaryalthough they may be used and do effect some economy of reagent. Theextent to which the desliming is to be effected is largely one ofeconomic compromise and the degree of desliming to produce optimumresults with minimum costs will be determined in the case of each ore.

The invention will be described in greater detail in conjunction withthe following specific example which illustrates typical modifications.

Example A low grade Minnesota iron ore containing about 14.5% Fe wasdeslimed, conditioned at high solids with sulfuric acid, varioussulfonated residues and an unsulfonated mineral oil, dilutecl to frothflotation density and floated. The sulfuric acid used was about 2 lbs.per ton with cottonseed still residues and bottoms and also lauric acidresidues, 4.0 lbs/ton with cottonseed pitch, 5.0 lbs/ton with wood oilresidues, 3.0 lbs/ton in the remainder of the tests. The cottonseedstill residues used in the first test were sulfonated with 50 parts of95.5% sulfuric acid per parts residues. In the second test, the

vegetable pitch was sulfonated with 67% of the same strength acid. Theother materials were treated with 67 parts of chlorosulfonic acid per100 parts residue. The chlorosulfonic acid was added. directly to theresidues in the third to glyceride oils and fatty acids, the amount ofcollector being suflicient to permit effective flotation, diluting theconditioned pulp to froth flotation density and subjecting it to frothflotation to produce a concentrate relatively rich in iron and a tailingrelatively poor in iron.

2. A method of beneficiating oxidized iron ores by froth flotation whichcomprises conditioning the ore at high solids with a collector and msulfuric acid, the amount of the acid being sufficient so that ondilution to froth flotation density without neutralization the pulp willhave a pH between 1.5 and 5.5, the effective collecting constituent ofthe collector being a sulfonated residue from the refining of glycerideoils and Conditioning- 0 oncentrate, gigs/{Fay percent, Fe Rough TailingSulfonated Product, Type Sulfo- Assay, nated 6 5 Assay Distrib percentpH Product Fe Cottonseed Still Residues 5. 2.83 53.33 82.67 2.81 2.7Vegetable Pitch 2. 0 4. 0 56. 82 86. 84 1. 73 2. 5 Talloel Bottoms. 4. 04. 0 56. 13 82.01 2. 42 2. 5 Coconut Bottoms 2. 0 4. 0 55. 32 87. 37 l.96 2. 6 Marine PitclL- 2. 0 4. 0 55. 09 90. 44 1. l5 2. 5 Linseed Pitch-2.0 6.0 58. 89 82.29 2.19 2. 5 Corn Oil Bottoms.. 10.0 4.0 55.90 92. 441.27 2.4 Laurie Acid Residues.... 10.0 4. 0 56.92 85. 70 2. 23 2. 5Vegetable Pitch 2. 0 4. 0 58. 78 80. 54 1.73 2. 5 VRO Residues 2. 0 4. 057.45 82. 43 l. 27 2. 6 Cottonseed Residues 2.0 4.0 55. 54 86. 53 1. 592.8 Linseed Residues... 2.0 4.0 53.83 72.23 3. 80 2.6 Soya Bean Residues2. 0 4. 0 57.98 82. 67 l. 48 2. 6 Tallow Residues. 2. 0 4. 0 57. 74 84.36 1. 38 2. 6 Wood Oil Residues. 10.0 4. 0 54. 40 80. 2, 53 2. 5 AnimalStill Residues. 2. 0 4. 0 59. 12 72. 78 3. 11 2. 6 Soft Steaiine Pitch2. 0 4. 0 57. 45 85.07 1. 27 2. 6 Cottonseed Foots 10. O 4. 0 57. 9781.35 3.11 2. 3 Fleshing Greaseby-product in glue mfg 2. 0 4. 0 59.3576. 84 2. 76 2. 6 Dark Cottonseed Distillate 2.0 4. 0 58.09 82.29 2. 302. 5 Dark Animal Distillate...- 2. 0 4. 0 57. 51 84. 13 1. 84 2. 5Linseed Still Residues... 2.0 4. 0 55. 78 77.86 2. 42 2. 6 2. (l 4. 058. 32 75. 90 2. 42 2. (i 2. 0 4. 2 58.09 78. 25 3.11 2. 6 5.0 4. 0 54.52 90. 28 1. 38 2. 4 4. 0 4. 4 56. 70 87. 95 1.50 2. 5 l0. 0 10.0 57. 5174. 42 2. 88 2. 5 Fatty Acid Pitch. 2. 0 5. 2 57. 63 87. 18 1. 73 2. 5Cottonseed Pitch. 3.0 4.0 56.92 78.03 2.76 2. 5 Fuel Oil #2 10.0 None Nouseful promotion. Fuel Oi1#2 4.0 2.0 Barren Froth Only.

The examples describe froth flotation operations as this is the mostimportant field in which the process of the invention can be used. Itshould be understood, however, that the process is also applicable inthe case of some collectors to other wet separation processes involvingagglomeration, for example, tabling, belt tabling and film flotation. Intabling operations, in general, more oiling agent should be used than infroth flotation.

In the claims the term oxidized iron ores is used in its commonlyaccepted meaning to include not only iron oxide ores such as thosecontaining magnetite, hematite, etc., but also hydroxides, carbonates,etc.

We claim:

1. A method of beneficiating oxidized iron ores by froth flotation whichcomprises conditioning the ore at high solids with a collector and aninorganic acid substance, the anion of which is a constituent of an acidhaving a dissociation constant of at least 10*", the amount of the acidsubstance being sufflcient sothat on dilution to froth flotation densitywithout neutralization the pulp will have a pH between 1.5 and 5.5, theefiective collecting constituent of the collector being a sulfonatedresidue from the refining of fatty acids, the amount of collector beingsuflicient to permit effective flotation, diluting the 55 3. A methodaccording to claim 1 in which the collector is associated with anunsulfonated oil as an oiling agent.

4. A method according to claim 2 in which the collector is associatedwith an unsulfonated oil as an oiling agent.

5. A method according to claim 2 in which the collector is a vegetableoil foot.

6. A method according to claim 5 in which the collector is associatedwith an unsulfonated oil as an oiling agent.

7. A method according to claim 2 in which the collector is a residuefrom the distillation refining of vegetable fatty acids.

8. A method according to claim 7 in which the collector is associatedwith an unsulfonated oil as an oiling agent.

9. A method according to claim 2 in which the collector is a residuefrom the distillation of marine oil fatty acids.

5 10. A method according to claim 9 in which the collector is associatedwith an unsulfonated oil as an oiling agent.

ROBERT BEN BOOTH. EARL CONRAD HERKENHOFF.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number UNITED STATES PATENTS Name Date Higgins Feb. 8, 1916 Number 8Name Date Nutter Feb. 8, 1916 Tartaron Jan. 18, 1938 Gillson Mar. 29,1938 Harris June 7, 1938 Carter Feb. 7, 1939 Trotter June 13, 1939 PatekOct. 12, 1943 Booth Sept. 18, 1945 Booth Oct. 29, 1946 Booth Oct. 29,1946

